It is known that numerous genera of bark beetles control the infestation of their host trees by giving off sex-specific pheromones [J.A.A. Renwick and J.P. Vite, Contrib. Boyce Thompson Inst. 24 (1970) 283].
The females of the Southern pine beetle Dendroctonus frontalis give off the bicylic ketal frontaline (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane) of the formula ##STR1## (I) as an aggregation pheromone, attract other male and female beetles of this genus and thus bring about a mass attack on the host tree. The attraction is synergistically intensified by the terpene alcohol trans-verbenol (trans-4,6,6-trimethylbicyclo-[3.1.1]hept-3-en-2-ol) of the formula ##STR2## and/or the monoterpene .alpha.-pinene of the formula ##STR3## (III). Mixtures of (I) with (II) or (III) are used under the name "FRONTALURE" and are prior art.
It is also known that the female beetles of the genus Dendroctonus ponderosae give off trans-verbenol (II) as an aggregation pheromone which together with terpenes attracts both sexes but predominantly males of the species (G.B. Pitman and J.P. Vite; Can. Entomol., 101 (1969) 143).
Mixtures of (II) with (III) and/or myrcene of the formula ##STR4## are used as attractants under the name "PONDELURE" and are prior art. The males of D. ponderosae give off exo-brevicomine (7-ethyl-5-methyl-6,8-diocabicyclo[3.2.1]octane) of the formula ##STR5##
(+)-exo-brevicomine (1R) (-)-exo-brevicomine (1S), endo-brevicomine (endo-7-ethyl-5-methyl-6,8-dioxabicyclo[3.2.1]octane]of the formula ##STR6##
(+)-endo-brevicomine (1R) (-)-endo-brevicomine (1S), and frontaline (I). Racemic exo-brevicomine (IV), endo-brevicomine (VI) and frontaline (I) reduce the catching power of the "PONDELURE" mixture (L.C. Ryker and L.M. Libbey; Chem. Ecolog. 8 (1982) 1399).
The infestation of the host trees is thus controlled by the interaction of female specific pheromone components such as frontaline (I) and trans-verbenol (II), and male-specific components such as exo-brevicomine (IV), endo-brevicomine (VI) and verbenone (4,6,6-trimethyl-bicyclo[3.2.1]hept-3-en-2-one) of the formula ##STR7##